This example uses WinIsMenuItemChecked to query the check attribute of a selected menu item before setting the check state of that menu item.

#define INCL_WINWINDOWMGR   /* Window Manager Functions   */
#include <os2.h>

USHORT  usItemId;           /* Menu item ID               */
HWND    hwndMenu;           /* Menu handle                */
BOOL    usChkstate;         /* New checked state          */
BOOL    fSuccess;           /* Success indicator          */
MPARAM  mp1;                /* Parameter 1 (menu item ID) */
MPARAM  mp2;                /* Parameter 2 (menu handle)  */

case WM_MENUSELECT:
     usItemId = SHORT1FROMMP(mp1);
     hwndMenu = HWNDFROMMP(mp2);

     /* Query the current check state */
     usChkstate = WinIsMenuItemChecked(hwndMenu, usItemId);

     /* Set the menu item check state */
     fSuccess = WinCheckMenuItem(hwndMenu, usItemId, usChkstate);